JP5105389B2 - Aluminum alloy manufacturing method - Google Patents

Abstract

An aluminum alloy fin stock of lower (more negative) corrosion potential and higher thermal conductivity is produced by a process, which comprises continuously strip casting the alloy to form a strip, cold rolling the strip to an intermediate gauge sheet, annealing the sheet and cold rolling the sheet to final gauge. Lower corrosion potential and higher thermal conductivity are imparted by carrying out the continuous strip casting while cooling the alloy at a rate of at least 300 DEG C./second, e.g. by conducting the casting step in a twin-roll caster.

Description

【００４２】
合金を、実験室スケールの二本ロールキャスターによって鋳造した。鋳造実験において、ストリップ試料を、4つの異なる速度で製造した。試料の表示および鋳造パラメーターを、以下の表２に示す。平均冷却速度（鋳造したままのストリップ厚みにわたる平均値としての速度）は、930℃/秒である。
【００４３】
【表２】

【００４４】
また、同じ化学組成（公称組成は、同じ。）を有する合金を、実験室スケールベルトキャスターによって鋳造した。実際の化学組成（重量％）は、Fe＝1.41、Mn＝0.39、Si＝0.83およびZn＝0.51である。鋳造したままのストリップの平均冷却速度は、53℃/秒である。
【００４５】
二本ロール鋳造試料および二本ベルト鋳造試料を、同じ方法によって鋳造後に、処理した。すなわち、これらの試料を、0.109 mmに冷間圧延し、400℃で2時間中間焼鈍し、次いで最終厚み0.06 mmに冷間圧延した。最終厚みのフィンストックを、標準ロウ付け試験加熱サイクルに付し、次いで伝導率および腐食電位について試験した。結果を、以下の表３にまとめた。
【００４６】
【表３】

【００４７】
以上の結果が示すように、二本ロール鋳造材料は、二本ベルト鋳造材料よりもより高い伝導率およびより低い腐食電位を有する。
【図面の簡単な説明】
【図１】 本発明の方法の好ましい態様における工程を示したフローチャート[0001]
(Technical field to which the invention belongs)
The present invention relates to a method for producing an improved aluminum alloy product used in the production of fins for heat exchangers, and finstock materials produced in this way, suitable corrosion potential and preferably high for the purpose. The present invention relates to a fin stock material having thermal conductivity.
[0002]
(Conventional technology)
Aluminum alloys have been used for many years in the manufacture of heat exchanger fins such as automotive radiators, condensers and evaporators. Traditional radiator fin alloys, as well shows the brazing proper and good sag resistance during brazing process, such a high strength after brazing process is obtained, it has been designed. Alloys used for this purpose usually contain manganese at high levels. An example of this alloy is the aluminum alloy AA 3003. With this alloy, good brazing performance can be obtained, but the thermal conductivity is relatively low. Low thermal conductivity has not been a serious problem so far because the thickness of the finstock material is significantly large. The fin stock material can transfer a large amount of heat if it has an appropriate thickness. However, To reduce the weight of the vehicle weight, it is necessary thinner fin stock material, which is a to emphasize the need for thermal conductivity improvement. Obviously, thinner materials tend to inhibit heat flow as they become thinner.
[0003]
Also, heat exchangers are designed to have good anticorrosion performance, which often produces fins from materials that have a lower corrosion potential (greater negative potential) than the rest of the heat exchanger. it (hence, fins to Rukoto corrosion resistance) can be achieved by, therefore, the fin material must be adjusted to the appropriate corrosion potential.
[0004]
Previously, the corrosion potential and the thermal conductivity of the alloy was been able variable by a change in the chemical composition of the alloy. For example, the present patent application of the inventors, to date, the special aluminum alloy, [by the applicant it has been found particularly suitable for use of the fin stock material, PCT Application WO 00/05426 (International Publication 2000 (Disclosed on February 3)]. This alloy contains Fe, Si, Mn and generally Zn and optionally Ti in a specific content range. However, improved corrosion potentials and improved thermal conductivity for heat exchangers made with fins made of this type of alloy make these and related alloys meet the stringent requirements of the current automotive industry. Seems to make it more useful.
[0005]
(Technical problem to be solved by the invention)
The object of the present invention is by means of physical means (ie physical means during finstock production) instead of or in addition to chemical means (ie chemical means by modification of alloy components). It is to improve the properties of aluminum alloy fin stock.
[0006]
Another object of the present invention is to provide an aluminum alloy finstock material that has a lower corrosion potential (greater negative potential) compared to an alloy having the same or similar chemical composition.
[0007]
Another object of the present invention is to provide an aluminum alloy finstock material having a low zinc content in the aluminum alloy and having a desired corrosion potential.
[0008]
Furthermore, another object of the present invention, other desirable properties, for example, while maintaining high strength and brazing aptitude, reduces the corrosion potential (is more negative) and / or thermal conductivity of the fin stock alloy Is to increase.
[0009]
(Disclosure of the Invention)
The present invention casts a finstock alloy to form the as-cast strip, which affects the corrosion potential and / or thermal conductivity of the resulting alloy product (ie, finstock alloy sheet material). It is based on the unexpected knowledge that it can. In particular, according to the present invention, casting an aluminum finstock alloy by a method that substantially increases the normal alloy cooling rate during a continuous casting process (eg, a two-roll casting process) results in a predetermined level in the prior art. the comparison to what was observed for the alloy components, the corrosion potential of the alloy can lower (can be Rukoto more negative potential), and / or that the thermal conductivity of the alloy can be higher, was found.
[0010]
Therefore, according to one aspect of the present invention, a method for producing an aluminum alloy plate fin stock material from a fin stock alloy comprising:
The method includes continuously casting a molten alloy to form an as-cast continuous strip, rolling the as-cast strip to form an intermediate-thickness alloy plate article, and an intermediate-thickness alloy plate. Annealing the article (hereinafter referred to as intermediate annealing), cold rolling the resulting intermediate thickness alloy sheet article to form a final thickness fin stock alloy sheet material;
During the continuous casting process, the alloy, even without least 300 ° C. / sec, preferably provides a method characterized by subjecting the average cooling rate of at least 500 ° C. / sec.
[0011]
Preferably, the continuous casting process is performed by a two-roll casting process that creates a cooling rate that falls within a desired range.
[0012]
The present invention also relates to an aluminum alloy finstock material produced by the method of the present invention.
[0013]
The alloy according to the present invention is an alloy having the following general composition (% by weight).
Fe 1.2-2.4% by weight
Si 0.5-1.1 wt%
Mn 0.3-0.6% by weight
Zn 0 ~ 1.0wt%
Ti (optional component) 0.005-0.040 wt%
Inevitable elements Each element less than 0.05% by weight, total amount ≦ 0.15% by weight
Al balance [0014]
More preferably, the alloy of the present invention has the following composition (wt%):
Fe 1.3-1.8 weight
Si 0.5-1.0 wt%
Mn 0.3-0.6 weight
Zn 0-0.7 weight
Ti (optional component) 0.005-0.020% by weight
Inevitable elements Each element less than 0.05% by weight, total amount ≦ 0.15% by weight
Al balance 【0015】
Preferably, to obtain a finstock alloy sheet material of good strength after brazing (high ultimate tensile strength (UTS)), cold rolling on the intermediate thickness strip after annealing is carried out so that the intermediate thickness alloy sheet is at least The thickness reduction is 45%, preferably at least 60%, preferably to a final thickness of 100 μm or less, more preferably 80 μm or less, and most preferably 60 μm ± 10%.
[0016]
The present invention is a fin stock material that provides good corrosion protection for heat exchangers using fin materials and is a brazed heat exchanger using thinner fins than was possible with the prior art A fin stock material suitable for manufacturing is provided. This can be achieved while maintaining sufficient fin strength and thermal conductivity to allow use in heat exchangers.
[0017]
In accordance with the present invention, a strip product formed from this alloy has an ultimate tensile strength (UTS) after brazing greater than about 127 MPa, preferably the ultimate tensile strength greater than about 130 MPa, after brazing greater than 49.0% IACS. Having a conductivity of greater than 49.8% IACS, most preferably greater than 50.0% IACS and a brazing temperature greater than 595 ° C, preferably greater than 600 ° C.
[0018]
This strip characteristic is measured under the simulated brazing conditions as follows.
[0019]
The ultimate tensile strength (UTS) after brazing is measured according to the following method simulating brazing conditions. A final processed fin stock of as-rolled thickness (eg, fin stock after rolling to a thickness of 0.06 mm) is placed in a furnace preheated to 570 ° C. and then heated to 600 ° C. in about 12 minutes, at 600 ° C. It was held for 3 minutes (soaked), cooled to 400 ° C. at 50 ° C./min, and then air cooled to room temperature. The material was then subjected to a tensile strength test.
[0020]
Thermal conductivity after brazing is the ultimate tensile strength (UTS) that simulates brazing conditions as conductivity (which directly corresponds to thermal conductivity and is easier to measure) about treated samples for the test, using the conductivity test method JIS-H0505 described measures. The conductivity was expressed as percentage of the international baked Dondo standards (International Annealed Copper Standard) (% IACS).
[0021]
Corrosion potential, with the sample treated as ultimate tensile strength (UTS) test in accordance with test method ASTM G3-89 described, using the Ag / AgCl / saturated KCl reference electrode, is measured.
[0022]
(Explanation of drawings)
FIG. 1 is a flowchart showing steps in a preferred embodiment of the method of the present invention.
[0023]
(Best Mode for Carrying Out the Invention)
As noted above, the present invention provides that the conditions under which the finstock alloy is cast, particularly the cooling rate during the casting process, is dependent on the specific physical properties of the finstock product, particularly the corrosion potential and thermal conductivity of the finstock product. It is based on the unexpected knowledge that it can influence. Thus, the present invention can be used to improve the above properties of a given finstock alloy without substantially adversely affecting other desired properties (eg, brazeability and strength after brazing). However, the present invention can advantageously ensure high strength using a specific rolling process after the annealing treatment, as described below.
[0024]
In the prior art, finstock alloy sheet materials have been manufactured using several methods, including direct chill casting, which has a relatively low cooling rate.
[0025]
However, high cooling rates can be achieved during certain types of continuous casting processes. For example, when casting an alloy with a two-roll caster for continuous strip casting with a thickness of 3-10 mm, the two-roll caster usually requires a cooling rate of 300-3,000 ° C./sec, which is significantly lower It has been found advantageous to cast the alloys according to the invention at such a high cooling rate in order to obtain a corrosion potential and / or a significantly higher thermal conductivity. Double roll casting is most often used to achieve such high cooling rates, but any form can be employed as long as it is a continuous strip caster that meets these requirements.
[0026]
The reason why the extremely rapid cooling rate during the casting process affects the corrosion potential and thermal conductivity of the finstock alloy is not exactly known. The change in corrosion potential is particularly noticeable and very surprising. The corrosion potential of the fin stock material is usually related to the zinc (Zn) content in the alloy, and the higher the zinc concentration, the more negative the corrosion potential value. However, according to the present invention, an improved low corrosion potential can be obtained at any zinc concentration, and an improvement is seen even if no zinc is present. Therefore, this action can be used to reduce the zinc content in the alloy while maintaining the original corrosion potential. Alternatively, the zinc content in the alloy can be maintained at the same or increased state to make the corrosion potential more negative with an amount greater than can be attributed to the increase in zinc content alone. it can.
[0027]
Also, the effect of two-roll casting on thermal conductivity is surprising in view of the fact that such thermal conductivity usually decreases as the solute content in the aluminum matrix of finstock alloys increases. is there. For example, rapid cooling during casting, as described above for two-roll casting, appears to increase the solution content in the metal matrix by forming a more supersaturated solution. Therefore, the thermal conductivity could be expected to decrease, while the opposite case was also seen.
[0028]
Despite these advantages, the faster cooling rates employed in accordance with the present invention during the casting process can be achieved in certain alloys by methods with slower cooling rates, such as the two belt casting method. Fig. 3 shows a tendency to produce fin stock materials having a particle size larger than the typical particle size for the fin stock material produced. If particles of larger particle size you remain in the alloy, the strength of the fin stock material after brazing may be smaller than the strength of the comparable two belt casting. Therefore, the as-cast strip produced according to the invention is preferably subjected to cold working (cold roll treatment) after reducing the particle size by intermediate annealing. Preferably, the intermediate thickness after intermediate annealing, which is preferably in the thickness range 100-600 μm, is at least 45%, more preferably at least 60%, most preferably at least 80% (final thickness) For example, the thickness is decreased by an amount in the range of 80 to 90%. Prior art finstock materials typically have a thickness of 80-100 μm, but at present, thinner stocks (eg, 60 μm ± 10%) of finstock alloys are desired. The necessary thickness reduction during the rolling process can be achieved by intermediate annealing and the required degree of cold rolling after the desired final thickness. For example, in order to produce a fin stock material with a final reduction thickness of 60 μm with a cold rolling reduction rate of 90%, the intermediate thickness strip after the intermediate annealing must have a thickness of about 600 μm, and thus the rolling before the intermediate annealing Is performed to achieve this degree of reduction from the as-cast strip thickness (usually 6-8 mm).
[0029]
In a continuous casting process, the average cooling rate generally refers to the cooling rate averaged over the thickness of the as-cast strip. The cooling rate at which a particular metal sample is subjected to casting can be measured from the average inter-dendritic cell spacing [see, eg, RE Spear et. Al .; the Transactions of the American Foundrymen's Society, Proceedings of the Sixty- Seventh Annual Meeting, 1963, Vol. 71, publisher: the American Foundrymen's Society, Des Plaines, Illinois, USA, 1964, p.209-215). An average value can be obtained by measuring a sample taken from each point over the thickness of the strip. When casting is performed by a two-roll casting method, a predetermined degree of hot rolling is performed during the casting process, and the dendrite structure can be a slightly compressed structure or a deformed structure. The dendrite arm spacing method can be used in such an environment, but is generally not necessary for two reasons. First, it can be assumed that casting by a two-roll caster usually causes cooling at a rate exceeding 300 ° C./second. Secondly, the two-roll casting method forms an as-cast strip where the temperature from the surface to the interior does not differ significantly at the exit of the caster. Thus, the surface temperature can be employed as the average temperature of the strip.
[0030]
The as-cast continuous strip (thickness 10 mm or less) produced as an intermediate of the present invention can generally be reduced in thickness by cold rolling alone. However, advantageously, some hot rolling can be used to reduce the thickness of the strip, from the as-cast (3-10 mm thickness) to the intermediate thickness (100- A reduction in thickness (600 μm) can be achieved by cold rolling alone or optionally by a combination of hot and cold rolling processes. However, unlike a direct-cooled casting ingot, the hot rolling process does not use or require any homogenization process in advance. If a hot rolling process is employed, the strip thickness can preferably be reduced to less than 3.0 mm.
[0031]
The alloy components are as described above. The characteristics obtained when various elements are introduced will be described below.
[0032]
The iron in the alloy forms intermetallic particles during the casting process, which are relatively small and contribute to particle strengthening. An iron content of less than 1.2% by weight is generally insufficient to form the desired number of reinforcing particles, while an iron content of more than 2.4% by weight forms large primary intermetallic phase particles. Can interfere with the rolling process to the desired very thin finstock thickness. The onset of these particle formations is exactly dependent on the use conditions of the casting process, and therefore preferably a good end product under the most widely possible processing conditions using iron in an amount of less than 1.8% by weight. Secure.
[0033]
In the alloy, silicon in the range of 0.5-1.1% by weight contributes to the strengthening of both particles and solid solutions. In general, silicon of less than 0.5% by weight is insufficient for this strengthening purpose, while silicon of more than 1.1% by weight can lower the conductivity. More importantly, at high silicon contents, the alloy melting temperature will drop to a temperature at which the material cannot be brazed. In order to obtain optimum strengthening, more than 0.8% by weight of silicon is particularly preferred.
[0034]
Manganese, when present in the range of 0.3 to 0.6% by weight, contributes significantly to solid solution strengthening and to some extent to material particle strengthening. If less than 0.3% by weight, the amount of manganese is insufficient for this purpose. Above 0.6% by weight, the presence of manganese in the solid solution has a significant adverse effect on the conductivity.
[0035]
The balance of iron, silicon and manganese contributes to achieving the desired strength, brazing performance and conductivity in the final material.
[0036]
Albeit at arbitrary, the zinc content may be present in an amount of up to 1.0 wt%, the fin material becomes lower corrosion potential (corrosion potential more negative). However, since the method of the present invention can reduce the corrosion potential, the amount of zinc can be reduced or eliminated while maintaining the same amount while lowering the corrosion potential. For many applications, at least about 0.1 weight percent zinc should be present in the alloy. In amounts above about 1.0% by weight, no commercially useful corrosion potential is obtained.
[0037]
Titanium, when present in the alloy as TiB _2, acts as a grain refiner during the casting process. If present in an amount greater than 0.04% by weight, titanium tends to adversely affect conductivity.
[0038]
For inevitable elements in the alloy, each element should be less than 0.05% by weight and the total amount should be less than 0.15% by weight. In particular, magnesium in an amount of less than 0.10% by weight, preferably should be present in an amount of less than 0.05 wt%, thereby, should ensure brazing suitability by N ocolok (TM) process. Copper must be maintained in an amount of less than 0.05% by weight. This is because copper exhibits a similar effect to that of magnesium and can cause pitting corrosion.
[0039]
An exemplary (preferred) casting process, rolling process and heat treatment process according to the present invention, including the final brazing process, is shown in FIG. 1 of the drawings attached hereto. This drawing shows the first step 1, in which a continuous roll with a thickness of 3 to 10 mm is formed by two-roll casting, and in this step a speed of 300 to 3,000 ° C./s is formed. With cooling in range. In the second step, the as-cast strip is rolled (hot rolling and / or cold rolling) to form an intermediate thickness of 100 to 600 μm. In the third step, the intermediate thickness strip is subjected to intermediate annealing at a temperature range of 350 to 450 ° C. for 1 to 4 hours. In the fourth step, the intermediate anneal strip is formed into a final thickness fin stock alloy sheet material, preferably at a thickness reduction rate of at least 45% (more preferably, a thickness reduction rate of 45-90%) to a thickness of 50-70 μm. Cold rolling. The fifth step is a brazing step performed during manufacture of a heat exchanger (for example, a radiator for an automobile), and the fin stock alloy plate material is attached to the cooling pipe during this step. This final process is usually performed by a radiator manufacturer so that the contours around the process are shown in different forms in the drawing.
[0040]
The casting process can be performed by various commercially available two-roll casters. Such casters are manufactured, for example, by Pechiney or Fata-Hunter. Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to this.
[0041]
(Example)
Casting experiments were conducted on alloys having the compositions shown in Table 1 below.
[Table 1]
: Alloy composition (wt%)

[0042]
The alloy was cast on a laboratory scale two roll caster. In casting experiments, strip samples were produced at four different speeds. Sample display and casting parameters are shown in Table 2 below. The average cooling rate (rate as an average over the as-cast strip thickness) is 930 ° C./sec.
[0043]
[Table 2]

[0044]
Also, alloys having the same chemical composition (the same nominal composition) were cast by laboratory scale belt casters. The actual chemical composition (% by weight) is Fe = 1.41, Mn = 0.39, Si = 0.83, and Zn = 0.51. The average cooling rate of the as-cast strip is 53 ° C / sec.
[0045]
Two roll cast samples and two belt cast samples were processed after casting by the same method. That is, these samples were cold-rolled to 0.109 mm, subjected to intermediate annealing at 400 ° C. for 2 hours, and then cold-rolled to a final thickness of 0.06 mm. The final thickness fin stock was subjected to a standard brazing test heating cycle and then tested for conductivity and corrosion potential. The results are summarized in Table 3 below.
[0046]
[Table 3]

[0047]
As the above results show, the two-roll cast material has a higher conductivity and lower corrosion potential than the two-belt cast material.
[Brief description of the drawings]
FIG. 1 is a flowchart showing steps in a preferred embodiment of the method of the present invention.

Claims (13)

A method of manufacturing an aluminum alloy plate fin stock material from a fin stock alloy,
The method continuously strips an alloy to form an as-cast strip, rolls the as-cast strip to form an intermediate thickness alloy plate article, Annealing and cold rolling the resulting intermediate thickness alloy sheet article to form a final thickness fin stock alloy sheet material;
The method consists of the following components: 1.2-2.4 wt% Fe, 0.5-1.1 wt% Si, 0.3-0.6 wt% Mn, 0.1-1.0 wt% Zn, less than 0.05 wt% of each inevitable element ( Performed on an alloy comprising a total of 0.15% by weight or less), and the balance aluminum,
The continuous strip casting process is performed while cooling the alloy at a rate of at least 300 ° C / second,
The resulting fin stock material has a conductivity greater than 49.0% IACS after brazing at a temperature greater than 595 ° C.   The method of claim 1, wherein the alloy further comprises 0.005 to 0.040 wt% Ti.   The method according to claim 1, wherein the method is performed on an alloy comprising the following components: 1.3-1.8 wt% Fe, 0.5-1.0 wt% Si, 0.3-0.6 wt% Mn, 0-0.7 wt% % Zn, 0.005-0.020 wt% Ti, less than 0.05 wt% of each inevitable element (total 0.15 wt% or less), and balance aluminum.   The method of claim 1, 2 or 3, wherein the alloy is cooled at a rate of at least 500 ° C / sec during casting.   The method according to any one of claims 1 to 4, wherein the thickness of the as-cast strip is 3 to 10 mm.   The method according to any one of claims 1 to 5, wherein the rolling step to the intermediate thickness of the strip is performed by a combination of hot rolling and subsequent cold rolling.   6. The method according to claim 1, wherein the rolling step to the intermediate thickness of the strip is performed by cold rolling alone.   The method according to claim 1, wherein the alloy is cast by a two-roll casting method.   9. The method according to any one of claims 1 to 8, wherein the intermediate thickness alloy sheet is cold-rolled to a final thickness at a thickness reduction rate of at least 45%.   10. The method according to any one of claims 1 to 9, wherein the intermediate thickness alloy sheet is cold-rolled to a final thickness at a thickness reduction rate of at least 60%.   The method according to any one of claims 1 to 10, wherein the finstock material has a conductivity greater than 49.8% IACS and an ultimate tensile strength greater than 127 MPa after brazing at a temperature greater than 595 ° C.   A fin stock material produced by the method according to claim 1. 13. The fin stock material according to claim 12 , wherein the thickness of the fin stock material is 60 μm ± 10%.

Images